E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Overall Description
1-85
Highband Path – Frequencies 3.2 GHz and Above
The output of the YIG oscillator (3.2 to 10 GHz) is routed to the A29 20 GHz Doubler microcircuit. Depending on the
desired output frequency, the signal is routed either through a bypass circuit (for frequencies below 10 GHz), or
through a frequency doubler circuit (for frequencies above 10 GHz). After the bypass or doubler circuits, the signal is
amplified and filtered.
In analog models, the A29 20 GHz Doubler output is routed to the A30 Modulation Filter. The A30 contains amplitude
and pulse modulators, amplifiers, and filters. In 40 GHz analog models, the A30 Modulation Filter output is routed to
the doubler path of the A27 40 GHz Doubler for frequencies above 20 GHz, and to a bypass switch in the A27 40 GHz
Doubler for frequencies up to 20 GHz. The output of the A27 40 GHz Doubler is connected to the A24 Highband
Coupler and A25 Highband Detector, the optional AT1 attenuator, and the front panel RF output connector.
In analog models with output frequencies above 40 GHz, the A30 Modulator filter provides outputs for the two
A36 Quadraplier inputs. One input is to a bypass circuit for frequencies from 250 KHz to 20 GHz. The other input
takes a 10 to 20 GHz signal and doubles it to provide 20 to 40 GHz to a second doubler for frequencies above 40 GHz.
The A36 Quadraplier’s output then connects to the A24 Highband Coupler and A25 Highband Detector, to the optional
AT1 attenuator, and to the front panel RF output connector.
In vector models, the 20 GHz Doubler output is routed to the A35 3–20 GHz I/Q Modulator and then to the
A30 Modulation Filter. The A35 3–20 GHz I/Q Modulator contains I and Q modulation circuits used to transfer I/Q
information to the RF signal.
In 20 GHz vector models, the output of the A30 Modulation Filter is routed to the A24 Highband Coupler and
A25 Highband Detector, then through the AT1 attenuator to the front panel RF output connector.
In 32 and 44 GHz models, the A35 3–20 GHz I/Q Modulator routes two signals. One signal goes to the A27 40 GHz
Doubler. The second signal goes to the IQ input of the A37 Upconverter. The output of the 40 GHz Doubler is then
routed to the LO side of the A37 Upconverter.
Lowband Path – Frequencies Below 3.2 GHz
For frequencies below 3.2 GHz, the YIG oscillator output is tuned between 4 and 8 GHz. In analog models and 20 GHz
vector models, the YIG oscillator output is routed to the A29 20 GHz Doubler microcircuit, where a portion of the
signal is coupled off and routed to the A6 Frac–N. In vector models with output frequencies > 20 GHz, the
A39 Coupler is added at the YIG oscillator output to couple the signal to the A6 Frac–N. A divider on the A6 Frac–N
divides the 4 to 8 GHz signal to a frequency between 250 MHz and 3.2 GHz. This signal is then routed to the A8
Output assembly where it is amplified, filtered and modulated.
NOTE The following paragraphs apply to E8257D instruments without Option 1EU, with serial
prefixes < US4928/MY4928/SG4928, and all E8267D & E8663B instruments.
Frequencies below 250 MHz are generated on the A8 Output by mixing the output signal from the A6 Frac–N (between
1000 and 750 MHz) with a 1 GHz LO from the A7 Reference. In vector models, the A8 Output also contains the I/Q
modulation circuit.
Option UNW (improved pulse performance below 3.2 GHz) adds a fast pulse modulator after the A8 Output.
> 3.2 GHz 3.2 to 10 GHz Highband path On all models, the 3.2 to 10 GHz oscillator output is doubled to achieve
frequencies between 10 and 20 GHz.
On analog models, the 10 to 20 GHz signal is doubled to achieve
frequencies between 20 and 40 GHz.
On vector models, frequencies between 20 and 44 GHz are developed
using a 40 GHz doubler and an upconverter. The 10 to 20 GHz signal from
the 20 GHz Doubler is doubled using the same 40 GHz Doubler used in
analog models, and then used as the LO input to the A37 Upconverter. A
3.2 to 10 GHz signal from the 20 GHz Doubler is fed to the IQ side of the
A37 Upconverter. Frequencies up to <28.5 GHz are the difference between
the LO and IQ inputs to the upconverter and frequencies 28.5 GHz to
44GHz are the sum.
In analog models with output frequencies >40 GHz, the output frequency
is developed by replacing the A27 40 GHz Doubler with the
A36 Quadraplier. The A36 Quadraplier doubles the 10 to 20 GHz signal to
develop frequencies up to 40 GHz and then doubles >20 GHz signals to
generate frequencies >40 GHz.
Output
Frequency
Oscillator
Frequency
Path Notes
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